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monad

monad

§(A 
type
, MA 
type
:monad monad.A monad.MA)
:
Any
 is
 
[Contains abstract features]

monad -- generic monad

A monad in X is just a monoid in the category of endofunctors of X, with
product × replaced by composition of endofunctors and unit set by the
identity endofunctor.

Don't be scared, in Java terms: A monad is a means to compose functions
applied to generic types.

Functions

§
:
Any
 => 
String 
[Inherited from  Any]
create a String from this instance. Unless redefined, `a.as_string` will
create `"instance[T]"` where `T` is the dynamic type of `a`
§
:
Any
 => 
Type 
[Inherited from  Any]
Get the dynamic type of this instance. For value instances `x`, this is
equal to `type_of x`, but for `x` with a `ref` type `x.dynamic_type` gives
the actual runtime type, while `type_of x` results in the static
compile-time type.

There is no dynamic type of a type instance since this would result in an
endless hierarchy of types. So for Type values, dynamic_type is redefined
to just return Type.type.
§(f Unary monad.MA monad.A)
:
Any
 => 
monad.MA 
[Abstract feature]
monadic operator within the same monad

Apply f to elements of type A and re-wrap them in this monad.
§(B 
type
, MB 
type
, f Unary (monad.infix >>=~.MB) monad.A)
:
Any
 => 
monad.infix >>=~.MB 
[Abstract feature]
monadic operator to another monad

Apply f to elements of type A and wrap them in MB.

NYI: This is currently useless since a redefinition is not
allowed for features with generic arguments. Is there a way
we could allow this anyway?
§(MMA 
type
:monad monad.MA (monad monad.A monad.MA), a monad.join.MMA)
:
Any
 => 
monad.MA 
[Abstract feature]
join operator

NYI: useless since redefinition currently not supported for
feature with generics.
§
:
Any
 => 
String 
[Inherited from  Any]
convenience prefix operator to create a string from a value.

This permits usage of `$` as a prefix operator in a similar way both
inside and outside of constant strings: $x and "$x" will produce the
same string.

Type Features

§
:
Any
 is
 
[Inherited from  Type]
string representation of this type to be used for debugging.

result has the form "Type of '<name>'", but this might change in the future

redefines:

§
:
Any
 is
 
[Inherited from  Type]
There is no dynamic type of a type instance since this would result in an
endless hierarchy of types, so dynamic_type is redefined to just return
Type.type here.

redefines:

§(T 
type
)
:
Any
 is
 
[Inherited from  Type]
Is this type assignable to a type parameter with constraint `T`?

The result of this is a compile-time constant that can be used to specialize
code for a particular type.

is_of_integer_type(n T : numeric) => T : integer
say (is_of_integer_type 1234) # true
say (is_of_integer_type 3.14) # false

it is most useful in conjunction preconditions or `if` statements as in

pair(a,b T) is

=>

or

val(n T) is

§
:
Any
 is
 
[Inherited from  Type]
name of this type, including type parameters, e.g. 'option (list i32)'.
§(a monad.type.A)
:
Any
 is
 
[Abstract feature]
return function
§
:
Any
 is
 
[Inherited from  Any]
Get a type as a value.

This is a feature with the effect equivalent to Fuzion's `expr.type` call tail.
It is recommended to use `expr.type` and not `expr.type_value`.

`type_value` is here to show how this can be implemented and to illustrate the
difference to `dynamic_type`.
last changed: 2024-09-18